Colonic bacteria clearly play a major role in the pathogenesis of major complications in patients with liver cirrhosis. By producing ammonia and endotoxins they can cause hepatic encephalopathy , and their translocation from the gut to the peritoneal cavity is the major mechanism for spontaneous bacterial peritonitis. There are also new studies suggesting a possible connection between bacterial translocation and bleeding from esophageal varices. Some of the therapeutic measures for the treatment and prevention of complications in cirrhotic patients, such as antibiotics and lactulose, are partially directed against gut bacteria.